What Is Homeostasis?

What Is Homeostasis?

Homeostasis refers to the body's need to reach and maintain a certain state of equilibrium. The term was first coined by a physiologist named Walter Cannon in 1926. More specifically, homeostasis is the body's tendency to monitor and maintain internal states, such as temperature and blood sugar, at fairly constant and stable levels.

How Is Homeostasis Maintained?

Your body has set points for a variety of states—including temperature, weight, sleep, thirst, and hunger. When the level is off (in either direction, too much or too little), homeostasis will work to correct it. For example, to regulate temperature, you will sweat when you get too hot or shiver when you get too cold.

Another way to think of it is like the thermostat in your house. Once set at a certain point, it works to keep the internal state at that level. When the temperature drops in your house, your furnace will turn on and warm things up to the preset temperature.

In the same way, if something is out of balance in your body, a physiological reaction will kick in until the set point is once again reached. Here's how the primary components of homeostasis work:

1. Stimulus: A stimulus from a change in the environment kicks something out of balance in the body.
2. Receptor: The receptor reacts to the change by informing the control unit.
3. Control unit: The control unit then communicates the change needed to bring the body back into balance.
4. Effector: The effector receives this information and acts on the change that is needed.

A negative feedback loop will work to decrease the effect of the stimulus, whereas a positive feedback loop will increase it. In homeostasis, negative feedback loops are most common, as the body is typically attempting to decrease the effect of the stimulus to get the body back to equilibrium.

Types of Homeostatic Regulation

There are three main types of homeostatic regulation that happen in the body. Though their names might be unfamiliar, you probably experience them every day.

Thermoregulation

When you think about homeostasis, temperature might come to mind first. It is one of the most important and obvious homeostatic systems. Regulating body temperature is called thermoregulation.

All organisms, from large mammals to tiny bacteria, must maintain an ideal temperature in order to survive. Some factors that influence this ability to maintain a stable body temperature include how these systems are regulated as well as the overall size of the organism.

• Endotherms: Some creatures, known as endotherms or "warm-blooded" animals, accomplish this via internal physiological processes. Birds and mammals (including humans) are endotherms.
• Ectotherms: Other creatures are ectotherms (aka "cold-blooded") and rely on external sources to regulate their body temperature. Reptiles and amphibians are both ectotherms.

Thermoregulation is also influenced by an organism's size, or more specifically, the surface-to-volume ratio. 

• Large organisms: Larger creatures have a much greater body volume, which causes them to produce more body heat.
• Small organisms: Smaller animals, on the other hand, produce less body heat but also have a higher surface-to-volume ratio. They lose more body heat than they produce, so their internal systems must work much harder to maintain steady body temperature. This is even true of babies, especially those born prematurely.

Osmoregulation

Osmoregulation strives to maintain the right amount of water and electrolytes inside and outside cells in the body. The balance of salt and water across membranes plays an important role, as in osmosis, which explains the name "osmoregulation." In this process, the kidneys are responsible for getting rid of any excess fluid, waste, or electrolytes. Osmoregulation also affects blood pressure.

Chemical Regulation

Your body regulates other chemical mechanisms as well to keep systems in balance. These use hormones as chemical signals—for example, in the case of blood sugar levels. In this situation, the pancreas would release either insulin, when blood sugar levels are high, or glucagon, when blood sugars are low, to maintain homeostasis.

Impact of Homeostasis

Homeostasis involves both physiological and behavioral responses. In terms of behavior, you might seek out warm clothes or a patch of sunlight if you start to feel chilly. You might also curl your body inward and keep your arms tucked in close to your body to keep in the heat.

As endotherms, people also have a number of internal systems that help regulate body temperature. When your body temperature dips below normal, a number of physiological reactions respond to help restore balance. Blood vessels in the body's extremities constrict in order to prevent heat loss. Shivering also helps the body produce more heat.

The body also responds when temperatures go above normal. Have you ever noticed how your skin becomes flushed when you are very warm? This is your body trying to restore temperature balance. When you are too warm, your blood vessels dilate in order to give off more body heat. Perspiration is another common way to reduce body heat, which is why you often end up flushed and sweaty on a very hot day.

Homeostasis and Mental Health

Like the body, the mind seeks its own type of homeostasis and attempts to compensate when out of balance. For example, one prominent theory of human motivation, known as drive-reduction theory, suggests that homeostatic imbalances create needs. These needs, in turn, motivate behavior in an attempt to restore homeostasis.